Life expansion
Vegetation :(See also: Day 3) ;443.8–419.2 million years ago The Silurian period was the first age to see megafossils of extensive terrestrial biota, in the form of moss-like miniature forests along lakes and streams. However, the land fauna did not have a major impact on the Earth until it diversified in the Devonian. The first fossil records of vascular plants, that is, land plants with tissues that carry water and food, appeared in the second half of the Silurian period. The earliest known representatives of this group are Cooksonia. Most of the sediments containing Cooksonia are marine in nature. Preferred habitats were likely along rivers and streams. Baragwanathia appears to be almost as old, dating to the early Ludlow (420 million years) and has branching stems and needle-like leaves of 10–20 cm. The plant shows a high degree of development in relation to the age of its fossil remains. Fossils of this plant have been recorded in Australia, Canada and China. Eohostimella heathana is an early, probably terrestrial, "plant" known from compression fossils of early Silurian (Llandovery) age. , p. 4 The chemistry of its fossils is similar to that of fossilised vascular plants, rather than algae. Climate change :(See also: Day 4) ;252 million years ago An unknown global warming event, in the nature of a , caused perhaps the most severe anoxic conditions in Earth's oceanic history. The was so sudden and severe, it triggered a series of events that caused "The Great Dying" ( ). There are several developing theories as to what contributed to the anoxic oceans: # , where increases in sea temperatures (and/or drops in sea levels) can trigger a catastrophic positive feedback effect on climate:: first, warming causes a sudden release of from compounds buried in seabeds and seabed permafrost; second, because methane itself is a powerful , temperatures rise further, and the cycle repeats. This runaway process, once started, could be as irreversible as the firing of a gun. #In 2015, evidence and a timeline indicated that the extinction was caused by events in the Large igneous province of the Siberian Traps. The eruptions, which occurred near coal beds and the continental shelf, triggered very large releases of carbon dioxide and methane. Another possible contributor to the extinction may have been from the aftermath of earlier from the in south-western China. #Anaerobic sulfur-reducing organisms, which dominated the chemistry of the oceans, caused massive emissions of toxic hydrogen sulfide. It was the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years. Studies in Bear Lake County near Paris, Idaho showed a quick and dynamic rebound in a marine ecosystem, illustrating the remarkable resiliency of life. Living creatures :(See also: Day 5) ;Great sea and land creatures (250–231.4 million years ago) About 10 million years after the Permian–Triassic extinction event, the "Great Dying" (252 mya), an explosion of a variety of fish, in the class of Teleost, appeared in the Early Triassic period. Additionally, after the quick and dynamic rebound of marine ecosystems, a diverse group of reptiles of the clade Dinosauria, appeared between 243 and 231 million years ago, The exact origin and timing of Dinosauria appearance is the subject of active research in academia. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods. In the mid-Jurassic period, around 170 million years ago, the appearance of bird-like dinosaurs (which lie outside class Aves proper), existed the Archaeopteryx. These were not capable of fully powered flight, many had toothy jaws and long bony tails, thus are classed in the broader group Avialae. ;Flying creatures (120 million years ago) True birds first appeared during the Cretaceous period, around 120 million years ago. DNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages. Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. ; End of Cretaceous period (66 million years ago) :* References Category:1 bya–67 mya Category:Theoretical History